Surface stress induced macroscopic and reversible strain effects have been observed for nanoporous metals in an electrochemical environment, according to conventional techniques, such as those disclosed in Science 300, 312 (2003) and Nano Lett. 4, 793 (2004). These macroscopic and reversible strain effects can be explained by changes of the surface electronic charge density through an applied potential relative to an electrolyte impregnating the pores. In particular, nanoporous platinum (Pt) and gold (Au) have been demonstrated to yield strain amplitudes comparable to those of commercial ferroelectric ceramics. Whether this charge-transfer induced macroscopic strain effect can be used to develop a new economically viable actuator technology will strongly depend on materials costs, efficiency, and long-term stability of the structures proposed. However, nanoporous noble metals such as nanoporous Pt and Au are heavy and costly, and are susceptible to degrading aging effects over time.
Therefore, it would be beneficial to reduce costs associated with developing, manufacturing, and using nanoporous metal actuators by using a less expensive material which improves the long-term stability of the structures produced, and enhances the mass-specific stored energy density by using more lightweight materials. Carbon based materials have been used in some applications, as disclosed in R. H. Baughman et al., Science 284, 1340 (1999), where carbon nanotubes were used for actuation. Although this is a light-weight material, it is only available in rope or sheet geometries and not as three dimensional bodies capable of shaping, forming, and molding to application specific dimensions, which prevents loading in compression. Furthermore, these materials at present are prohibitively costly. Therefore, they do not currently present a viable solution to the above described problems.